Effects of coupling strength of the electron-photon and the photon-environment interactions on the electron transport through multiple-resonances of a double quantum dot system in a photon cavity

TL;DR

This study investigates how varying the electron-photon and photon-environment coupling strengths affect electron transport in a double quantum dot system within a photon cavity, revealing complex resonance behaviors and current modulation.

Contribution

It provides a detailed analysis of multi-resonance effects and transport properties in a multilevel DQD system coupled to a photon cavity, highlighting the impact of coupling strengths and photon energy regions.

Findings

Photon energy anti-crossings lead to multiple Rabi-resonances and a current dip.

Increasing electron-photon coupling displaces Rabi-resonance states and reduces the current dip.

Enhancing cavity-environment coupling increases current at intermediate photon energies by weakening Rabi-resonances.

Abstract

We study electron transport properties through a double quantum dot (DQD) system coupled to a single mode photon cavity, DQD-cavity. The DQD system has a complex multilevel energy spectrum, in which by tuning the photon energy several anti-crossings between the electron states of the DQD system and photon dressed states are produced, which have not been seen in a simple two level DQD system. Three different regions of the photon energy are studied based on anti-crossings, where the photon energy ranges are classified as "low", "intermediate", and "high". The anti-crossings represent multiple Rabi-resonances, which lead to a current dip in the electron transport at the "intermediate" photon energy. Increasing the electron-photon coupling strength, $g_\gamma$, the photon exchanges between the anti-crossing states are changed leading to a dislocation of the multiple Rabi resonance states. Consequently, the current dip at the intermediate photon energy is further reduced. Additionally, we tune the cavity-environment coupling, $\kappa$, to see how the transport properties in the strong coupling regime, g$_{\gamma}>\kappa$, are changed for different directions of the photon polarization. Increasing $\kappa$ with a constant value of $g_\gamma$, a current enhancement in the intermediate photon energy is found, and a reduction in the current is seen for the "high" photon energy range. The current enhancement in the intermediate photon energy is caused by the weakening of the multiple Rabi-resonance in the system.